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Good question Brock. It seems the roundel was in use pre-war for the Dutch aircraft, but the orange triangle was the standard marking of the Dutch East Indies Army aircraft along with orange rudders. Both were entirely separate arms. In Wesworld the orange triangle on its side marks a squadron leaders aircraft and the roundel is standard (indeed all aerial forces are part of a unified Royal Netherlands Air Force).

My first draft impressions on the first jet-propelled aircraft of the Netherlands. I'm open to opinions and suggestions. They use SAE jet data from Hoo and are roughly contemporary with real world designs and are based firmly on existing airframe technology. The in-service dates might be slightly optimistic but service entry would most likely be to training units etc. and deliveries are dependant on supplies from SAE.

Fokker D.XXIIIS
An experimental jet-powered variant based on a standard D.XXIIIE airframe. The engine was obtained from the SAE, a VB.03/ Rayton Swazi rated at 3,000lbs thrust. This was mounted in the rear fuselage with two lateral intakes in the inner wing roots. Both piston engines were removed and a new streamlined nosecone fitted. The tailbooms were strengthened and the tailplane moved to the tips of the tailfins to clear the exhaust. A pressurised cockpit was fitted too. The second D.XXIIIE prototype was rebuilt from December 1944 and made its first flight with a pre-production VB.03 engine rated at 2,800lbs on 17 May 1945. It was re-engined with an early production Rayton Swazi engine in December. Flight testing continued until August 1946.
Length: 10.56 m (34 ft 6 in)
Span: 11.88 m (39 ft 0 in)
Wing Area: 303 ft2
Wingloading: 37.9 lb/ft2
Empty Weight: 3526 kg (7,773 lb)
Maximum Weight: 5500 kg (12,125 lb)
Powerplant: 1x 2,800lb Rayton VB.03 or 3,000lb Rayton Swazi centrifugal turbojet engine
Maximum Speed: 843 km/h (524mph)
Service ceiling: 12450 m (41,000 ft)
Rate of climb: 19.7 m/sec (3,877 ft/min)
Range: 917 km (570 miles)
Armament: none

Koolhoven F.K.62
As the Royal Netherlands Air Force began looking at jet-powered fighters, it also saw the need to experiment with high-speed jet-powered fast bombers. Koolhoven took their F.K. 61 and simply removed the piston engines and fitted two 3,000lb Rayton Swazi centrifugal turbojets in revised nacelles. A production airframe was converted in September 1945 and made its first flight on 29 December as the F.K.61S. A series of eight pre-production aircraft designated F.K.62 followed from February 1946. These differed in having a new tail unit with more dihedral on the tailplanes and more streamlined nose. The new main undercarriage retracted into the inner wingroots. The two crewmen were seated on Danish ejector seats, the navigator/ bomb-aimer sitting in the nose. Production of 135 F.K.62s began in September 1946. 36 were completed as F.K.62R high-altitude reconnaissance aircraft with five cameras fitted in the former bomb bay.
Wingspan: 21.34 m (80 ft 0 in)
Length: 15.03 m (49 ft 3 in)
Height: 5.73 m (18 ft 8 in)
Wing area: 66.03 m2 (710 ft2)
Gross weight: 15043 kg (33,164 lb)
Max take-off weight: 17250 kg (38,030 lb)
Powerplant: 2x 3,000lb Rayton Swazi centrifugal turbojet engines
Maximum speed: 716 km/h (445 mph) at 12192 m (40,000 ft)
Service ceiling: 13106 m (43,000 ft)
Range: 2414 km (1,500 miles) internal fuel
Armament: 2000kg (4,409 lb) of bombs in an internal bomb bay and 1000 kg (2,204 lb) externally or 12x 75mm rocket projectiles underwing

The D.XXIIIS looks rather like the OTL Saab J21R, so taking that as an exemplar, I find that the D.XXIIIS is heavier by half a ton, has slightly less engine power, yet is a tad faster, with superior ceiling and a somewhat greater range. Perhaps some minor adjustment to performance to bring it in line with the J21R would be worth considering. Beyond that, the concept appears reasonable.

The D.XXVIII's stats look reasonable enough, but I really have to wonder if the development cycle of proposed for it allows for sufficient experience with the D.XXIIIS to know what is necessary. As to the design, looks good to me.

The F.K.62 is problematic for me, if only because I have doubts about the viability of taking an airframe designed for piston engines (and piston speeds) and merely slapping a couple of jet engines on it. The Russians tried that with a number of designs and the results were of doubtful utility (the Tupolev Tu-12 comes to mind). I won't say it cannot be done, but I'd like to know more about the design history.

Yes, the XXIIIS is based on the OTL Saab J21R in spirit though I didn't actually look at the specs when I wrote this! So I'm glad I got close. I'll edit the range and ceiling.

The XXVIII is basically a Vampire rip-off but in all-metal. I agree the timings are close. The problem is the Netherlands can see Britain and Germany and now France with operational jets and newer models in development. SAE jet tech is perhaps slightly behind the curve and this design will morph into a DH Venom clone by 1950, by which time it'll make a fine fighter. There is urgency to get a jet fighter and so development is on priority. Also, I'm not sure how much the XXIIIS will contribute, most piston conversions in OTL only proved they were bad idea and I'd like to think having built the excellent basic D.XXIII series that Fokker has the aerodynamic know-how to develop the Vampire-esque airframe. Jets pose problems but SAE testbeds are airborne now and one hopes some design data comes with those engines. However, I might push the dates back ~6 months.

The F.K.61 is based on the never-built DH.102 'Super Mosquito'. When the DH.102 was designed there were brief sketch plans for a jet powered version. No specs have ever been found, only the plan. So my design takes that other approach and brings it to life, specs are a mash-up of Ar 234 and reduced Canberra/ early Westland design version before Petter moved to EE.
Early jet bombers generally are tricky, they were either; a) small twin-engine types with limited payload and range, b) four engine small mediums (B-45), c) big multi engine. I don't think of the first generation jet bombers were any good, the second gen Canberra and Il-28 were good but needed 6,000lb+ engines to work well. So the FK.62 is basically an early attempt to increase bomber speed and is a compromise. It'll work but it won't be great, I might degrade the specs a little more. Perhaps in 1950 Koolhoven will work on a proper Canberra clone?

I agree with you whole-heartedly on the question of first-generation jet bombers - the designs that emerged were either very light on their ordnance loads or were rather klunky agglomerations of engine nacelles. Even some of the more aerodynamic "paper napkin" designs you'll find at Luftwaffe '46 have engines hung on some very odd places, or they are limited to 1,000 kg for 1,000 km. The problem is engines.

I've deliberately slowed the development of the BMW003 engine though it will begin to make its appearance in late 45/early 46 - starting at about 3,000 pounds of thrust and scaling up from there rather quickly - the basic design has a lot of development potential. At some point I may release some "sketch designs" of things the airframe manufacturers are proposing but it will be 1947-48 before any metal - if any at all - would be cut on them.

It would be helpful to gauge Dutch jet developments against those in the SAE, where the engine technology seems to be originating. However...

Fokker S.XV
A development of the S.XI Instructor first flown in May 1948 powered by a 260hp Minerva-Avia Minion Minor piston engine with a maximum speed of 265 km/h (164 mph). First deliveries were made in December 1948.

Koolhoven F.K.62
As the Royal Netherlands Air Force began looking at jet-powered fighters, it also saw the need to experiment with high-speed jet-powered fast bombers. Koolhoven took their F.K. 61 and simply removed the piston engines and fitted two 3,000lb Rayton Swazi centrifugal turbojets in revised nacelles. A production airframe was converted in September 1945 and made its first flight on 29 December 1946 as the F.K.61S. A series of eight pre-production aircraft designated F.K.62 followed from February 1947. These differed in having a new tail unit with more dihedral on the tailplanes and more streamlined nose. The new main undercarriage retracted into the inner wingroots. The two crewmen were seated on Danish ejector seats, the navigator/ bomb-aimer sitting in the nose. Production aircraft were powered by two 4,200lb VB.04 Stuart Zulu centrifugal turbojets. Production of 135 F.K.62s began in January 1948. 36 were completed as F.K.62R high-altitude reconnaissance aircraft with five cameras fitted in the former bomb bay.
Wingspan: 21.34 m (80 ft 0 in)
Length: 15.03 m (49 ft 3 in)
Height: 5.73 m (18 ft 8 in)
Wing area: 66.03 m2 (710 ft2)
Gross weight: 15,043 kg (33,164 lb)
Max take-off weight: 17,250 kg (38,030 lb)
Powerplant: 2x 4,200lb VB.04 Stuart Zulu centrifugal turbojet engines
Maximum speed: 716 km/h (445 mph) at 12192 m (40,000 ft)
Service ceiling: 13106 m (43,000 ft)
Range: 1610 km (1,000 miles) internal fuel
Armament: 2000kg (4,409 lb) of bombs in an internal bomb bay and 1000 kg (2,204 lb) externally or 12x 75mm rocket projectiles underwing

Stichting voor de Ontwikkeling en Bouw van een Experimenteel Hefschroefvliegtuig (Foundation for the Development and Construction of an Experimental Helicopter (SOBEH)
Founded in August 1948 to foster research and development of Dutch helicopters. This initiative was launched with the support of the NLL, NIV and RSL.

Nurtanio Wiweko Glider N.V.
Founded in May 1946 by Wiweko Soepono, Nurtanio Pringgoadisurjo, and J. Sumarsono in a workshop in Magetan, near Madiun, DEI. The company designs and builds gliders.
Currently in Production:
Zögling
NWG-1
In Development:
WEL-X – motorised glider with a Harley Davidson engine, first flown in March 1948

Something new being worked on by Koolhoven and which should fly in early 1949.
This is inspired by the Sud Est SE.117 Volttigeur, and the experiences of the Ubangi-Shari conflict.
Photo for illustrative purposes.

Koolhoven F.K.65
In 1948 the Luchtmacht raised a requirement for an overseas ground support aircraft capable of fulfilling counter-insurgency, observation and ground attack roles. The requirements drew on the lessons from operations in Ubangi-Shari. The aircraft was to be twin-engined, able to loiter at low altitude for five hours, operate from rough strips and carry six paratroopers. Armament would be fixed cannon, bombs and rockets. Koolhoven responded with the F.K.65 which was chosen for development. The twin-engined low-wing aircraft carried an observer/bombardier in a glazed nose compartment with the pilot in a cockpit behind, both protected by armour plating. The rear fuselage could carry six paratroopers or light freight and there was a door in the lower port-side of the fuselage. The fixed armament was fitted in two lower fuselage blister packs. A rugged tricycle undercarriage was used and the engine nacelles were also armoured. The first of two prototypes first flew on 21 January 1949 and production began that summer, the first aircraft entering service in January 1950. 115 were ordered.
Wingspan: 18.00m (59ft 0.5in)
Length: 12.61m (41ft 4.5in)
Height: 4.5m (14ft 7in)
Wing area: 41.8m2 (449.5sq ft)
Gross weight: 6,950kg (15,322lb)
Powerplant: 2x 750hp Minerva Minion VI
Maximum speed: 430km/h (267mph)
Range: 1,300km (807 miles)
Service ceiling: 8,000m (27,550ft)
Armament: 2x 23mm GAST cannon in lower fuselage, two wing racks for up to 500kg bombs and four wing racks for 50kg bombs or 4-8x rockets underwing

In addition to the Koolhoven F.K.65 above, new aircraft flying for the first time or entering service during 1949 will be:

Entering Service

Fokker D.28A
This is a variant of the basic D.XXVIII jet fighter design developed for the Royal Netherlands Air Force East Indies Command (KLNI). The main differences are; stronger undercarriage, improved cockpit air conditioning, greater generator capacity, hardpoints capable of carrying up to 500kg each and a more powerful 3,500lb Swazi 4 turbojet. 115 were ordered in July 1948 and deliveries began in September 1949.

Koolhoven F.K.62R
This is a variant of the F.K.62 jet bomber equipped as an high-altitude reconnaissance aircraft with five cameras fitted in the former bomb bay. 36 will be built.

In Development

De Schelde S.27
The S.27 was designed as a purpose-built anti-submarine aircraft with a secondary role of torpedo strike to replace the Koolhoven F.K.59 and also be capable of use aboard aircraft carriers. The four-seat aircraft was developed to be as compact as possible. The internal torpedo bay was capable of carrying two heavy or two lightweight torpedoes or four depth-charges. Six underwing hardpoints could carry rocket pods, depth charges or up to four additional torpedoes. A ventrally mounted retractable radome for Phillips AS-3 RDF and a tail mounted Magnetic Anomaly Detector (MAD) were fitted. A 70 million candlepower searchlight was mounted on the starboard wing. 60 explosive charges dispensed ventrally were used with the Phillips ADS-1 detection set. Smoke floats and marine markers could also be carried. Two prototypes and 15 production aircraft were ordered on 30 June 1947 and the first prototype made its maiden flight on 4 December 1949. The first production aircraft will enter service in early 1951.
Crew: four (two pilots, two detection systems operators)
Length: 13.26 m (43 ft 6 in)
Wingspan: 22.12 m (72 ft 7 in)
Height: 5.33 m (17 ft 6 in)
Wing area: 45.06 m² (485 ft²)
Empty weight: 8,310kg (18,315 lb)
Loaded weight: 10,630 kg (23,435 lb)
Maximum take-off weight: 11,860 kg (26,147 lb)
Powerplant: 2x 1,575hp Minerva Faucon XIX 14-cylinder radial engines
Maximum speed: 450 km/h (280 mph) at sea level
Cruise speed: 240 km/h (150 mph)
Range: 2,170km (1,350 miles) or 9 hours endurance
Service ceiling: 6,700 m (22,000 ft)
Armament: total of 2,200 kg (4,800 lb) carried in the internal bomb bay and six underwing hardpoints comprising, torpedoes, depth-charges, bombs, mines or 75mm and 120mm rocket pods.

During 1949 the Luchmacht will also take delivery of 24 SH.40 Tourbillon helicopters during 1949 to form at least one operational squadron and a training unit.
No final decision has yet been reached on an order for the smaller scouting helicopter.